Why Is Gypsum Added to Cement?

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The terms cement and concrete are used interchangeably, although cement is actually an ingredient of concrete. Gypsum is often added to cement and concrete to slow down the drying time. Cement dries quickly and retarding that process allows workers to pour the mixture into the various forms or frames needed.

What is Gypsum

Gypsum is a naturally occurring mineral mined from deposits formed by ancient seabeds as a raw material. Composed of calcium sulfate and water, it is used for a variety of manufacturing, industrial, and agricultural uses. An important property of gypsum is that it is naturally fire-resistant.

How Cement is Made

Cement is produced from a chemical combination of calcium, silicon, aluminum, iron and small amounts of other ingredients that are carefully measured to get the right result. Often gypsum is added during the final grinding process since it helps regulate how long the concrete takes to set. Cement is fine in texture and one pound of cement contains 150 billion grains.

Mixing Cement and Gypsum

You can use a pre-mixed product combining the cement ingredients with the right amount of gypsum. You can also mix them yourself. As soon as you add water to the mix, the hardening process begins. The first part of this process is called the dormant period, and lasts up to halfway through the drying process. This is when concrete can be placed into forms. The paste soon will become too stiff to work with.

Uses of Pre-Mixed Gypsum and Cement

Gypsum cements possess considerably greater strength and hardness than standard industrial plasters. Also, gypsum cements require less water for mixing and the casts they produce are easier to paint, heavier, less porous, and more durable. These cements produce more heat while setting. Given these properties, gypsum cements are often used to make statuary and other art objects like lamp bases and craft projects.

Safety Tips

Whether working on a construction site or laying a patio for your backyard, some basic protections is needed. Safety glasses or goggles help keep the fine dust from blowing into your eyes. Cement is alkaline in nature, so wet caustic concrete and other cement mixtures are harmful to skin. Protective clothing like long pants, long sleeves and waterproof gloves is necessary.